A wide variety of electric power supplies have been developed for use with integrated circuit and other devices. Some common examples include DC/DC converters and VRMs. In many applications, including those utilizing low voltage digital circuitry such as microprocessors, the power supply must provide a fast dynamic response to changes or variations in the load or load requirements.
A typical DC/DC converter converts a DC voltage supplied from one or more power sources to a desired voltage. This can be accomplished using switching devices that selectively couple one or more current sources either to the power supply output or to a return. By dynamically controlling the on/off timing of each switching device, the number of current sources supplying current to the output, and thus the amount of output current supplied to the load, can be dynamically controlled. This is particularly useful when the load current demand varies and the output voltage is desired to remain within a particular range or a nominal value.
When the load on the output becomes low, the amount of current switched to the return (referred to as circulating current) increases. These circulating currents typically remain active and thus available for dynamic switching from the return to the output in response to an increase in the load.
As recognized by the inventors hereof, one disadvantage of many known power supplies is the amount of power that is consumed or wasted by circulating current. As such, the inventors have identified a need for a power supply having reduced low load power losses while maintaining a satisfactory dynamic response to changing load requirements.